Production for nuclear fuel assemblies requires significant care during fabrication. The fabrication steps taken for such fuel assemblies is often costly and complicated due to the amount of precautionary steps that are required. Nuclear fuel rods are designed with several different components, wherein each of the components having a specific design purpose. The fissionable component of each nuclear fuel rod is generally a uranium enriched ceramic material (a uranium oxide) that is shaped in the form of a pellet. Individual pellets are placed end to end to form a fuel column. The fuel column is then inserted into an elongated rod made of corrosion resistant metal, such as a zirconium alloy, called a fuel clad. The fuel column is protected from mechanical and chemical wear by the fuel clad. The fuel clad protects the fuel column during operation of the reactor as well as handling of the fuel assembly. As an additional precaution, springs and/or other devices are also included inside the volume encapsulated by the fuel clad to allow the uranium fuel elements to swell and shift within prescribed limits in the fuel clad. This allows the fuel column to withstand several different loading scenarios without detrimental effects to the fuel column. The completed fuel rods are then stored. Completed fuel rods are then placed in a parallel arrangement, called a fuel assembly, to prevent the fuel rods from contacting each other during use.
In current automated loading systems, nuclear fuel pellets are taken from a fuel pellet elevator and transferred by a conveyor in a tray to a segment make-up table. The fuel pellets are removed from the fuel pellet tray by a worker and placed on the table. The fuel pellets are placed in a parallel orientation and then compacted by a pusher device to form columns of uranium containing ceramic material. The pushing device is connected to a linear variable displacement transducer which is configured to provide an electrical output signal. The electrical output signal is then read by a computer and an overall length of the individual fuel element column is determined. A computer then compares an overall design specification for the fuel rod with the overall length determined from the output signal. If the difference between the expected design value of the nuclear fuel element column length and the measured value meets a predetermined threshold value, the fuel rod cladding is then loaded with the nuclear pellet column. If the overall length of the fuel pellet column is outside of the threshold value, the fuel pellets are then rejected from the segment make-up table. A top end cap is then welded on the existing open side of the fuel rod cladding thereby completing the nuclear fuel rod.
There is a need to provide an apparatus and method which will enable an operator to perform additional quality assurance checks of the nuclear fuel elements during the manufacturing process of a nuclear fuel rod.
There is also a need to provide a method and device to load nuclear fuel pellets into a nuclear fuel rod in a safe, economical and non-damaging manner.
There is a further need to provide a method and device which will load cylindrical fuel pellets into an open fuel rod clad, i.e. a fuel rod clad without a lower plug welded to the fuel clad.
There is a further need to provide a method and device which will allow cylindrical fuel pellets to be loaded into an open fuel rod clad to eliminate slow insertion speeds for pellet placement found in existing methods and systems.